The contract should expressly regulate precise allocation of accessories, exclusive use rights and delivered keys or access devices. General wording is not enough where the point is material for price, use or implementation.
Important tools are maturity conditions, escrow release, assurances and withdrawal rights. This prevents payment from being released while decisive evidence is still missing.
Without clear wording, disputes arise after handover about parking, cellar, garden areas or ongoing costs. That is why the point belongs in the contract before signing, not only in later correspondence.